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Code Issues Activity Actions

Piano: Use a secondary thread to write the audio stream.

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This frees up the main thread to draw the GUI. The secondary thread uses
a pipe to trick the main thread's event loop to break out of select() and
update() the PianoWidget. :^)
This commit is contained in:
Andreas Kling 2019-07-13 20:20:08 +02:00
parent dcfa93e71f
commit eec9666735
3 changed files with 88 additions and 54 deletions
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87
Applications/Piano/PianoWidget.cpp
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@ -8,6 +8,8 @@ PianoWidget::PianoWidget()
{
memset(keys, 0, sizeof(keys));
m_bitmap = GraphicsBitmap::create(GraphicsBitmap::Format::RGB32, { m_width, m_height });
m_front_buffer = new Sample[2048];
m_back_buffer = new Sample[2048];
}
PianoWidget::~PianoWidget()
@ -18,16 +20,44 @@ void PianoWidget::paint_event(GPaintEvent& event)
{
GPainter painter(*this);
painter.add_clip_rect(event.rect());
painter.blit({ 0, 0 }, *m_bitmap, m_bitmap->rect());
painter.fill_rect(event.rect(), Color::Black);
auto* samples = m_front_buffer;
Color wave_color;
if (m_wave_type == WaveType::Sine)
wave_color = Color(255, 192, 0);
else if (m_wave_type == WaveType::Saw)
wave_color = Color(240, 100, 128);
else if (m_wave_type == WaveType::Square)
wave_color = Color(128, 160, 255);
int prev_x = 0;
int prev_y = m_height / 2;
for (int x = 0; x < m_sample_count; ++x) {
double val = samples[x].left;
val /= 32768;
val *= m_height * 2;
int y = (m_height / 2) + val;
if (x == 0)
painter.set_pixel({ x, y }, wave_color);
else
painter.draw_line({ prev_x, prev_y }, { x, y }, wave_color);
prev_x = x;
prev_y = y;
}
render_piano(painter);
render_knobs(painter);
}
void PianoWidget::fill_audio_buffer(uint8_t* stream, int len)
{
size_t sample_count = len / sizeof(Sample);
m_sample_count = len / sizeof(Sample);
memset(stream, 0, len);
Sample* sst = (Sample*)stream;
for (size_t i = 0; i < sample_count; ++i) {
auto* sst = (Sample*)stream;
for (int i = 0; i < m_sample_count; ++i) {
static const double VOLUME = 3000;
for (size_t n = 0; n < (sizeof(m_note_on) / sizeof(bool)); ++n) {
if (!m_note_on[n])
@ -58,52 +88,24 @@ void PianoWidget::fill_audio_buffer(uint8_t* stream, int len)
static Queue<Sample*> delay_frames;
static const int delay_length_in_frames = 50;
//assert((int)sample_count == m_width);
if (m_delay_enabled) {
if (delay_frames.size() >= delay_length_in_frames) {
auto* to_blend = delay_frames.dequeue();
for (size_t i = 0; i < sample_count; ++i) {
for (int i = 0; i < m_sample_count; ++i) {
sst[i].left += to_blend[i].left * 0.333333;
sst[i].right += to_blend[i].right * 0.333333;
}
delete[] to_blend;
}
Sample* frame = new Sample[sample_count];
memcpy(frame, sst, sample_count * sizeof(Sample));
Sample* frame = new Sample[m_sample_count];
memcpy(frame, sst, m_sample_count * sizeof(Sample));
delay_frames.enqueue(frame);
}
GPainter painter(*m_bitmap);
painter.fill_rect(m_bitmap->rect(), Color::Black);
Sample* samples = (Sample*)stream;
Color wave_color;
if (m_wave_type == WaveType::Sine)
wave_color = Color(255, 192, 0);
else if (m_wave_type == WaveType::Saw)
wave_color = Color(240, 100, 128);
else if (m_wave_type == WaveType::Square)
wave_color = Color(128, 160, 255);
int prev_x = 0;
int prev_y = m_height / 2;
for (int x = 0; x < (int)sample_count; ++x) {
double val = samples[x].left;
val /= 32768;
val *= m_height * 2;
int y = (m_height / 2) + val;
if (x == 0)
painter.set_pixel({ x, y }, wave_color);
else
painter.draw_line({ prev_x, prev_y }, { x, y }, wave_color);
prev_x = x;
prev_y = y;
}
render_piano(painter);
render_knobs(painter);
ASSERT(len <= 2048 * (int)sizeof(Sample));
memcpy(m_back_buffer, (Sample*)stream, len);
swap(m_front_buffer, m_back_buffer);
}
double PianoWidget::w_sine(size_t n)
@ -351,3 +353,12 @@ void PianoWidget::render_knobs(GPainter& painter)
painter.draw_rect(wave_knob_rect, Color(r, g, b));
painter.draw_text(wave_knob_rect, wave_name, TextAlignment::Center, Color(r, g, b));
}
void PianoWidget::event(CEvent& event)
{
if (event.type() == CEvent::Custom) {
dbg() << "Piano got custom event!";
update();
}
GWidget::event(event);
}